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4.11 gears

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 90K5, Jun 19, 2000.

  1. 90K5

    90K5 1/2 ton status

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    My K5 currently has 3.42 gears:( and 33" BFG ATs I want to put 4.11 gears in it but I'm not sure about some things. Will 85mph be better or worse for it than it is now and will my mpg be better or worse. I mean my true mpg not whatever the odometer says. Also how expensive is it for the dealer or someone else to correst the speedo/odo?
     
  2. BigBadBowTie

    BigBadBowTie 1/2 ton status

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    With 4.11:1 gears you'll run a higher RPM at 85 mph, than with 3.42:1 gears.. I'll assume you have an overdrive tranny, which should put you at about 2200RPM's at 85mph.

    It cost's about $100 to get a spedo recalibrated, you'll have to find a local spedo shop,they usually calibrate state vehicles. When I get home from work, I'll scan an article Igot from one of the off-road magazines, that explains spedo recalibration, you may be able to do it youself for underr $10 & <10 Min.

    Finnally, gas milage, it's a hard call, on one hand you'll be running higher rpm's on the freeway, but you won't haveto change gears as often, on the other hand it takes less torque to leave a stop light. I'd have to say your gas milage would improve.

    Rick
    86 K-5
    http://www.BigBadBowTie.ColoradoK5.com
     
  3. jcg

    jcg 1/2 ton status

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    Correcting the speedo is easy. Once you get everything done, have a friend drive at 55mph and see what your speedo reads. Go to the dealership and they can get a new speedo gear for you (about $8 at my local chevy dealer) based on how far your speedo is from 55. You might need a new aluminum insert that holds the gear too, there's two different sizes. The insert should only cost about $20 if you need a new one. Changing the gear only takes about 10 minutes and is really easy to do. You'll have to pull the speedo gear before you go to the dealership so you can find out how many teeth it has on it (usually stamped on the side or just count them). Each tooth on the gear represents 2mph on the speedo so if your speedo is low you want fewer teeth to make it spin faster.

    For example, my speedo was 10mph low at 55 (read 45) after my new tires were put on. I had a 40 tooth gear so I got one with 35 teeth and the longer aluminum holder. It took longer to get my tools out than it did to actually change the gear.

    Hope this helps, it got a little longer than I had planned.

    Joe
    Rochester Institute of Technology Team Mini-Baja
    88 Jimmy
     
  4. 90K5

    90K5 1/2 ton status

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    hey jcg thanks but where is the speedo gear? is it in the dash or the tranny or tcase? Thanks for the info i'm not going to the dealer now except to but the part.
     
  5. BigBadBowTie

    BigBadBowTie 1/2 ton status

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